How does natural selection lead to evolution? A. Environmental changes favor weaker members of the species
B. Overproduction provides food for the strong members of the species
C. Helpful variations accumulate among surviving members of a species
D. Stronger offspring kill weaker members of a species

d)Through evolution, periwinkle populations with a history of predation by crabs have become less vulnerable to crab predation.

Explanation:

It seems apparent that the periwinkle snails with softer shells were in the are that were not preyed by the crabs. These snails did not have a selective pressure and thus the shells remains soft/missing and on the forced encounter with the crabs they were instantly consumed.

In contrast,  the snails that had been in co-existence with the crabs had developed a harder shell because those that did not have a solid shell were unable to survive predation. These individuals did not reproduce and that trait did not pass on. If it did, these were consumed by the crabs.

Meanwhile, the snails with thicker shells were not preyed upon by the crabs and were able to survive to pass along the genes that preserved them.

As time went on the selective pressure put on the snails by the crabs changed the phenotype and resulted in a resistant variety in the are where the crabs were.